logic circuits

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hates

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i am making a infrared burglar alarm using logic circuits but i want to have a digital display how is it possible?
 
hi,
What do you need to display digitally on your alarm system?

Numbers or just LED's ?
 
If you want to display characters, take a look at 7segment displays and a BCD to 7segment decoder. If you use multiplexers you can even drive a number of these 7segment displays off a single BCD to 7segment decoder.
One of these decoders is the 74LS47.
 
I think you could use a comparator like LM393 and use (I think you can use a phototransistor for I-RED right?) a I-red LED and a phototransistor and compare voltage when they walk by. I dunno might work
 
The time of each burglar entry?

Yes time can be displayed. Anything can be displayed.

How many burglars are you expecting?
 
Displaying the time will need you to get a very accurate clock signal somewhere. This will also require you to increase the number of counters in your circuit to get the clock to the correct frequency. Maybe you should take a look at a PIC then. If you want to take the challenge and only use logic circuits, try this:
Depending on the country where you live your AC mains supply have a pretty steady frequency. (50Hz or 60Hz) Extract this signal and use it as you clock.
Just an idea
 
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